What is the recommended IV (intravenous) dosing of hydralazine (hydrazine) for hypertensive urgency?

IV Hydralazine Dosing for Hypertensive Urgency

The recommended IV dosing of hydralazine for hypertensive urgency is an initial dose of 10 mg via slow IV infusion (maximum initial dose 20 mg), which can be repeated every 4-6 hours as needed. 1, 2

Administration and Monitoring

• Administration method: Slow IV infusion directly into the vein 3, 2
• Onset of action: 10-30 minutes 1
• Duration of action: 2-4 hours 1
• Blood pressure monitoring:
  • BP should be checked frequently after administration
  • BP begins to decrease within 10-30 minutes of administration
  • The average maximal decrease occurs in 10-80 minutes 2

Clinical Considerations

Efficacy and Limitations

• Hydralazine is effective in lowering blood pressure but has unpredictable responses and a prolonged duration of action 1
• Due to this unpredictability, hydralazine is not considered a desirable first-line agent for acute treatment in most patients with hypertensive urgency 1
• The FDA-approved oral dosing range is 100-200 mg daily in 2-3 divided doses, with a 2:1 (oral:IV) conversion ratio when transitioning from oral to IV 1, 3

Side Effects and Precautions

• Common side effects include:

  • Reflex tachycardia
  • Sodium and water retention
  • Headache
  • Flushing
  • Vomiting 1

• Hydralazine is associated with drug-induced lupus-like syndrome at higher doses 1, 3

• Due to sodium and water retention and reflex tachycardia, it should be used with a diuretic and beta blocker 1

Special Populations

• Hydralazine is particularly useful in eclampsia and preeclampsia 1, 4
• Certain patients (especially those with marked renal damage) may require a lower dose 2
• In pediatric patients, although not established in controlled clinical trials, the usual recommended parenteral dosage is 1.7 to 3.5 mg/kg of body weight daily, divided into four to six doses 2

Important Cautions

• The product should be used immediately after the vial is opened 2
• It should not be added to infusion solutions 2
• Hydralazine may discolor upon contact with metal; discolored solutions should be discarded 2
• In cases of increased intracranial pressure, lowering blood pressure may increase cerebral ischemia 2
• When other potent parenteral antihypertensive drugs are used in combination with hydralazine, patients should be continuously observed for several hours for any excessive fall in blood pressure 2

Management Algorithm

1. Initial dose: 10 mg via slow IV infusion (maximum initial dose 20 mg)
2. Monitoring: Check blood pressure frequently after administration
3. Repeat dosing: May repeat every 4-6 hours as needed
4. Transition to oral therapy: Most patients can be transferred to oral hydralazine within 24-48 hours 2
5. Adjunctive therapy: Consider adding a diuretic and beta blocker to counteract sodium/water retention and reflex tachycardia 1

By following these guidelines, clinicians can effectively and safely use IV hydralazine for management of hypertensive urgency while minimizing potential adverse effects.